(a) Field of the Invention
The present invention relates to a system for filtering particulates.
(b) Description of the Related Art
The control of particulate emissions from diesel engines is one of the major technical issues facing the automotive industry, especially in light of tightened regulations on vehicle particulate emissions. Under EURO-5 for example, a set of standards for pollutant emissions from diesel and petrol cars, stricter limits are being placed on the concentration of certain nitric oxides (NOx), carbonized hydrogen (HC), and particulate matter. The regulations will be broadened to cover, amongst other aspects, the weight, size, and amount of particulates generated. A host of other countries outside Europe is likewise concerned about the health and environmental hazards posed by particulate emissions and in search of ways to tackle this problem. Accordingly, there is a need in the art for filtering apparatuses to reduce particulate matter in exhaust gas.
Most conventional diesel particulate filters (DEF) capture particulates that are over 10 μm in diameter. This is a significant limitation given that the average particulate matter in vehicle exhaust gas, e.g. from diesel powered engines, is under 2.5 μm in diameter, thereby escaping filtration and releasing into the air. Smaller particulate matters can remain airborne longer, which increases their potential for harm to the environment and public health.
While conventional methods for removing particulates exist, they suffer from a variety of drawbacks. For instance, the use of filters having minute pores can lead to increased exhaust gas pressure over the filter and the manufacturing of such filters involve a difficult catalyst coating process.
Another filtering method operates on an apparatus that agglomerate particulate matter and that is situated at a front exhaust pipe connecting the engine to the diesel particulate filter. The disadvantage to this method lies in the agglomeration of particulate matter of non-uniform size, thus resulting in increased exhaust gas pressure and clogged front exhaust pipe. The formation of large particles from non-spherically shaped particulates can also disrupt the flow of exhaust gas. The front exhaust pipe is also prone to oxidization, which can lead to deterioration in the pipe structure.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.